The skies over California's Mojave Air and Space Port are serving as the proving ground for the WhiteKnightTwo, the massive mothership being tested to air-launch commercial spaceliners on suborbital flights.

A third test flight of the huge carrier craft — whichlooks like a giant catamaran for the sky — is deemed as "imminent", said Will Whitehorn, President of Virgin Galactic — the company put into business by U.K. adventurer and billionaire Richard Branson and his Virgin Group, created

WhiteKnightTwo's builders, the Mojave spaceport-based Scaled Composites, unveiled the spacecraft mothership on July 28, 2008. That rollout was followed by a Dec. 21 maiden flight with another scurry into the sky taking place in early February.

While the third flight of the vehicle is close at hand, "we never give a date in advance as we only take off in light winds and generally good weather at this stage in an experimental program," Whitehorn told SPACE.com.

WhiteKnightTwo (WK2) will haul the suborbital SpaceShipTwo spaceliner to a high-altitude release point. That spaceship, the first of which is nearing completion, has moved from drawings to hardware thanks to the Scaled Composites work force under the watchful eye of the firm's founder, Burt Rutan - now Chief Technology Officer and Chairman Emeritus of the company.

Roaring to life via a hybrid rocket motor, SpaceShipTwo will carry two pilots and six passengers on a suborbital trajectory, scooting the rubber-necking "rush hour" commuters to the edge of space and returning them to terra firma at $200,000 a seat.

Whitehorn said that testing of the WK2 carrier plane — christened "Eve" in honor of Richard Branson's mother — has gone well.

"We now have just under four hours flying on WhiteKnightTwo and have now gone above 18,000 feet," Whitehorn said. "We are very pleased with progress so far and it would be fair to describe her performance so far as flawless," he added.

The up-and-coming next test flight is set to raise the bar in altitude and flight-duration of the vehicle, Whitehorn said, among other items.

Aircraft heading: Oshkosh, Wisconsin
For those hungering for an up close and personal look at WhiteKnightTwo, best head for the Experimental Aircraft Association's AirVenture extravaganza being held July 27-Aug. 2 in Oshkosh, Wisc.

After successfully completing its initial flight test program, space launch vehicle Virgin Mothership (VMS) Eve is slated to make its "world public debut" there on July 27.

The space launch vehicle will arrive as part of the opening-day air show.

AirVenture attendees are being promised opportunities for up-close viewing of the vehicle on the ground each day until its departure flight as part of the Saturday, Aug. 1 air show. Event organizers and Virgin Galactic officials are also scoping out additional showcase flights during the week.

Whitehorn pointed out that VMS Eve is not only being designed to lift SpaceShipTwo. The Virgin Galactic business case for space also includes unmanned satellite launch or doubling as a space science vehicle, as well as an astronaut training craft.

According to Whitehorn, Virgin Galactic plans to conduct test flights of VMS Eve carrying SpaceShipTwo during the second half of 2009.